Going by the database on this site, Wii has the most retail platformers, with PS3 in second and 360 in third. Including the online services (WW, PSN and XBL), 360 has 185 (21 retail and 164 XBL), Wii had 95 (Wii 63 and WW 32), and PS3 has 184 (PS3 32 and PSN 152).
The problem with this is it includes games that haven't been released and includes games from all regions (it might also include cancelled games). Now, with the PS3, it includes PSN releases of PSP games, so they don't count because you can't play PSP games directly from your PS3. Also, games that people might not consider platformers are also on the list (Symphony of the Night, for example). It also seems that some DLC is included with the lists (the DLC for Prince of Persia 2008, for example).
